Method for separating entrained aqueous from loaded organic in an SX process

ABSTRACT

A method for separating a lighter liquid from a heavier liquid according to one embodiment of the present invention may comprise the following steps. First, the lighter liquid and the heavier liquid may be introduced into a settling tank and thereafter allowed to form a first upper liquid fraction and a first lower liquid fraction. The first upper liquid fraction may comprise the lighter liquid with residual amounts of the heavier liquid contained therein. The first upper liquid fraction is then decanted into a trough. The first upper liquid fraction decanted into the trough is then allowed to form a second upper liquid fraction and a second lower liquid fraction. The second lower liquid fraction may comprise the heavier liquid with residual amounts of the lighter liquid contained therein. The second lower liquid fraction is thereafter drained from the trough and allowed to form a third upper liquid fraction and a third lower liquid fraction.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a division of co-pending U.S. applicationSer. No. 09/193,210, filed Nov. 17, 1998, which is incorporated hereinby reference for all that it discloses.

FIELD OF INVENTION

[0002] This invention relates to solvent extraction processes in generaland more specifically to a process for separating the organic phase fromthe aqueous phase in a solvent extraction process for removing copperfrom raw ore.

BACKGROUND

[0003] The overall efficiency of a copper mining operation depends inpart on the techniques which are used to separate the copper from theraw ore. Many different methods have been developed over time toaccomplish copper removal with a maximum degree of effectiveness. Ofprimary interest are various techniques which are collectively known as“solvent extraction,” or “SX” for short, in which copper ions areleached or otherwise extracted from raw ore using chemical agents.Solvent extraction processes for removing copper ions are described indetail in U.S. Patent No. 5,733,431, entitled “Method for RemovingCopper Ions from Copper Ore Using Organic Extractions” which isincorporated herein by reference for all that it discloses.

[0004] Most solvent extraction or SX processes currently being used inthe copper industry utilize a multi-stage process in which the raw oreis first contacted with an initial leaching solution or lixiviant.Representative lixiviants include, but are not limited to, sulfuricacid, acidic chloride solutions, nitrate solutions, ammonia, andammonium salt compositions. The lixiviant leaches copper ions from theore to generate a lixiviant product which consists of a copper ionconcentrate (also known as a “pregnant leach solution”). The lixiviantproduct/copper ion concentrate is thereafter combined (e.g., mixed) withan organic extractant. The organic extractant removes the copper ionsfrom the lixiviant product to generate a copper ion-rich organicsolution. Many different organic extractants exist and may be obtainedfrom any of a wide variety of commercial sources. By way of example,most commercially available organic extractant compositions typicallyconsist of a mixture containing about 90-95% of a petroleum dilutant(e.g., kerosene or tridecanol) and about 5-10% hydroxyphenyl oxime.Prior to the combination of the organic extractant and the lixiviantproduct, the organic extractant will contain little or no copper ionstherein (depending on whether a fresh or recycled extractant supply isinvolved) and is also known as a “barren organic extractant.” During themixture of these components, copper ions within the lixiviant productare transferred directly into the barren organic extractant. As aresult, an organic phase and an aqueous phase are produced. The organicphase (also known as a “loaded organic extractant”) consists of theorganic extractant which contains copper ions extracted from thelixiviant product. The aqueous phase (also known as a “raffinate”)consists of the lixiviant solution which lacks any substantial orappreciable amounts of dissolved copper therein. The organic phase isthereafter separated from the aqueous phase and is retained for furtherprocessing to extract the copper. The aqueous phase (i.e., raffinate)may be discarded, stored for future use, or immediately reused onadditional amounts of ore.

[0005] A significant problem associated with the foregoing processrelates to the separation of the organic phase (i.e., the loaded organicextractant) from the aqueous phase (i.e., the raffinate). While the twophases tend to separate into discrete layers based on substantialdifferences in polarity and other physical factors (e.g., specificgravity), as a matter of practice, some aqueous tends to remain with theloaded organic extractant and vice-versa. The presence of the aqueousphase in the organic phase can cause problems later on during theelectrowinning process in which the copper is plated onto a cathode. Forexample, in some SX processes, the presence of the aqueous phase in theorganic phase has the effect of transferring chloride into the pregnantelectrolyte. In other processes, aqueous entrainment in the loadedorganic has the effect of transferring iron to the pregnant electrolyte.Each contaminate has a negative effect on cathode quality, dictates ahigh plant bleed, and cuts production while increasing costs.

[0006] Partly in an effort to solve some of the foregoing problems, someSX processes have resorted to the use of coalescers in an attempt toperform an additional separation of the aqueous phase from the organicphase. While such coalescers are generally effective in removingadditional amounts of entrained aqueous from the loaded organic, theyare expensive and can be difficult to operate.

SUMMARY OF THE INVENTION

[0007] A method for separating a lighter liquid from a heavier liquidaccording to one embodiment of the present invention may comprise thefollowing steps. First, the lighter liquid and the heavier liquid may beintroduced into a settling tank and thereafter allowed to form a firstupper liquid fraction and a first lower liquid fraction. The first upperliquid fraction may comprise the lighter liquid with residual amounts ofthe heavier liquid contained therein. The first upper liquid fraction isthen decanted into a trough. The first upper liquid fraction decantedinto the trough is then allowed to form a second upper liquid fractionand a second lower liquid fraction. The second lower liquid fraction maycomprise the heavier liquid with residual amounts of the lighter liquidcontained therein. The second lower liquid fraction is thereafterdrained from the trough and allowed to form a third upper liquidfraction and a third lower liquid fraction.

BRIEF DESCRIPTION OF THE DRAWING

[0008] Illustrative and presently preferred embodiments of the inventionare shown in the accompanying drawing in which:

[0009]FIG. 1 is a side view in elevation of the liquid separationapparatus for separating a lighter liquid from a heavier liquid;

[0010]FIG. 2 is front view in elevation of the first trough and weirassembly showing the position of the first lighter fraction drain andthe two sump drains;

[0011]FIG. 3 is a side view in elevation of one of the sump drains; and

[0012]FIG. 4 is a schematic flow diagram illustrating the liquidseparation apparatus as it may be used in a solvent exchange process toseparate an organic phase from an aqueous phase.

DETAILED DESCRIPTION OF THE INVENTION

[0013] Liquid separation apparatus 10 for separating a lighter liquidfrom a heavier liquid is shown and described herein as it could be usedto separate an organic phase (i.e., the lighter liquid) from an aqueousphase (i.e., the heavier liquid) in a solvent extraction process forremoving copper from raw ore. Alternatively, the liquid separationapparatus and method according to the present invention could be used inany of a wide range of other processes wherein it is necessary ordesirable to separate a lighter liquid from a heavier liquid.

[0014] Referring to FIGS. 1 and 2, the liquid separation apparatus 10according to one preferred embodiment of the present invention maycomprise a settling tank 12 sized to receive a mixture of a lighterliquid 14 and a heavier liquid 16. By way of example, in one preferredembodiment, the lighter liquid 14 may comprise a “loaded organicextractant” (i.e., the organic phase) whereas the heavier liquid 16 maycomprise a “raffinate” (i.e., the aqueous phase). The settling tank 12effects a first or primary separation of the lighter liquid 14 from theheavier liquid 16 in a quiescent zone 18. The lighter liquid 14generally rises to the top of the quiescent zone 18 and forms a firstupper liquid fraction 20, whereas the heavier liquid 16 settles to thebottom of the quiescent zone 18 and forms a first lower liquid fraction22. In most applications, a first interface 24 forms between the upperand lower liquid fractions 20 and 22.

[0015] It should be noted that in most applications, a completeseparation of the lighter and heavier liquids 14 and 16 generally willnot occur in the settling tank 12. Accordingly, the upper liquidfraction 20 will also generally include residual amounts of the heavierliquid 16. That is, the upper liquid fraction 20 will generally compriseprimarily the lighter liquid 14, but with residual amounts of theheavier liquid 16 entrained therein. Similarly, the lower liquidfraction 22 will generally comprise primarily the heavier liquid 16, butwith residual amounts of the lighter liquid 14 entrained therein.

[0016] A weir 30 positioned adjacent the outlet end 28 of the settlingtank 12 extends above the level of the first interface 24 separating thefirst upper and lower liquid fractions 20 and 22. Weir 30 allowssubstantially the first upper liquid fraction 20 to be removed (i.e.,decanted) from the settling tank 12. A trough 26 positioned adjacent theweir 30 receives the first upper liquid fraction 20 discharged over theweir 30 and performs a secondary separation of the lighter and heavierliquids 14 and 16. That is, trough 26 permits the first upper liquidfraction 20 drawn from the settling tank 12 to separate into a secondupper liquid fraction 20′ and a second lower liquid fraction 22′. Asecond interface 24′ may form between the second upper and lower liquidfractions 20′ and 22′. As was the case for the first settling tank 12,the separation of the lighter and heavier liquids 14 and 16 effected intrough 26 is generally not complete. That is, the second lower liquidfraction 22′ will generally comprise primarily the heavier liquid 16,but with residual amounts of the lighter liquid 14 contained therein.

[0017] Referring now primarily to FIG. 2, the first trough 26 may beprovided with a first lighter fraction drain 38 having an inlet end 40located at an elevated position above the floor 42 of trough 26. In onepreferred embodiment, the elevated inlet end 40 of the first drain 38 islocated above the second interface 24′ contained within trough 26.Accordingly, the elevated inlet end 40 of first drain 38 removes fromthe trough 26 substantially the second upper liquid fraction 20′. Thesecond upper liquid fraction 20′ may thereafter be directed to a lighterfraction container 62 (FIG. 1) and held for further processing, as willbe described in greater detail below. Trough 26 may also be providedwith a pair of sump drains or traps 44 and 46 located on the bottom 42of trough 26. The sump drains 44 and 46 are used to remove substantiallythe second lower fraction 22′ from the trough 26.

[0018] Each sump drain 44, 46 may be connected to a respective columnseparator 48, 50 (FIG. 1), each of which performs a tertiary separationof the lighter and heavier liquids 14 and 16. That is, each columnseparator 48, 50 permits the second lower liquid fraction 22′ drawn fromthe trough 26 to form a third upper liquid fraction 20″ and a thirdlower liquid fraction 22″. The first column separator 48 may be providedwith a lighter fraction return line 52 for returning to the trough 26quantities of the third upper liquid fraction 20″. Column separator 48may also be provided with a drain line 54 for draining the third lowerliquid fraction 22″ from the column separator 48. In one preferredembodiment, the drain line 54 from column separator 48 may be connectedto a second settling tank 56. The second column separator 50 may beessentially identical to the first column separator 48 and may comprisea lighter fraction return line 58 for returning to the trough 26quantities of the third upper liquid fraction 20″. A drain line 60 maybe used to drain to the second settling tank 56 the third lower liquidfraction 22″ from the second column separator 50.

[0019] In the embodiment shown and described herein, the second settlingtank 56 may be used to perform a quaternary separation of the lighterand heavier liquids 14 and 16. That is, the second settling tank 56permits the third lower liquid fraction 22″ drawn from the columnseparators 48 and 50 to separate into a fourth upper liquid fraction20″′ and a fourth lower liquid fraction 22″′. The fourth upper liquidfraction 20″′ may thereafter be directed to the lighter fractioncontainer 62 and held for further processing. The fourth lower liquidfraction 22″′ which comprises primarily the heavier liquid 16 (e.g., theaqueous phase or raffinate) may be withdrawn from the second settlingtank 56 and reused or discarded, depending on the requirements of theparticular process.

[0020] The liquid separation apparatus 10 may also be provided with aheavier fraction container or tank 32 that is fluidically connected tothe settling tank 12 so that the first lower liquid fraction 22 from thesettling tank 12 flows into the heavier fraction container or tank 32.In one preferred embodiment, the container 32 may be provided with asecond weir 34 which, together with the container 32, defines a secondtrough 36. The second trough 36 may be provided with a drain 64 forremoving the heavier liquid 16 from the second trough 36. The heavierliquid 16 (e.g., the aqueous phase or raffinate) withdrawn from thesecond trough 36 may be combined with the heavier liquid 16 withdrawnfrom the second settling tank 56 and reused or discarded, as the casemay be.

[0021] Operation of the liquid separation apparatus 10 according to thepresent invention may be understood by considering its operation in asolvent extraction (i.e., SX) process of the type that may be used toremove copper from raw ore. Referring now to FIG. 4, the first step insuch a process typically involves contacting the raw ore with an initialleaching solution or lixiviant. In one preferred embodiment, thelixiviant may comprise primarily the heavier liquid 16 or raffinaterecovered by the liquid separation apparatus 10. Additional amounts ofnew lixiviant added, if necessary, to compensate for process losses. Thelixiviant leaches copper ions from the raw ore to generate a lixiviantproduct or “pregnant leach solution” 11. Thereafter, the pregnant leachsolution 11 may be combined with a barren organic extractant 13 in asuitable mixing container 15. During the mixture of these components,copper ions contained in the pregnant leach solution 11 are transferreddirectly into the barren organic extractant 13. As a result, an organicphase (e.g., the lighter liquid 14) and an aqueous phase (e.g., theheavier liquid 16) are produced. The organic phase comprises primarilythe loaded organic extractant (which contains copper ions captured fromthe pregnant leach solution). The aqueous phase (also known asraffinate) comprises primarily the lixiviant solution which lacks anysubstantial or appreciable amounts of dissolved copper therein.

[0022] In the foregoing SX process, the organic phase is generally lessdense than the aqueous phase and the two phases tend to separate intodiscrete layers based on substantial differences in specific gravity andother physical factors (e.g., polarity). However, as a matter ofpractice, some of the aqueous phase (i.e., the raffinate) tends toremain with the organic phase (i.e., the loaded organic extractant). Theliquid separation apparatus 10 according to the present invention isused to separate the aqueous and organic phases.

[0023] Referring back now to FIG. 1, the pregnant leach solution 11 maybe combined with the appropriate quantity of barren organic extractant13 in a suitable mixing container 15. A mixer or agitator 17 may be usedto mix together the pregnant leach solution 11 and the barren organicextractant 13. During mixing, copper ions contained in the pregnantleach solution 11 are transferred to the barren organic extractant 13,resulting in the formation of the organic phase (i.e., the lighterliquid 14) and the aqueous phase (i.e., the heavier liquid 16). The twophases (i.e., the organic and aqueous) resulting from the mixture of thepregnant leach solution 11 and barren organic extractant 13 arethereafter allowed to enter the settling tank 12. In the quiescent zone18, the organic phase (i.e., the lighter liquid 14) begins to separatefrom the aqueous phase (i.e., the heavier liquid 16). The result of theseparation is the formation of the first upper liquid fraction 20 andthe first lower liquid fraction 22. In the example SX process shown anddescribed herein, the first upper liquid fraction 20 will consistprimarily of the organic phase with residual amounts of the aqueousphase contained therein, whereas the first lower liquid fraction 22 willconsist primarily of the aqueous phase with residual amounts of theorganic phase contained therein.

[0024] The first weir 30 permits the first upper liquid fraction 20contained within the quiescent zone 18 of settling tank 12 to bedecanted into trough 26. The trough 26 effects a secondary separation ofthe organic and aqueous phases by allowing the first upper liquidfraction 20 drawn from the settling tank 12 to separate into a secondupper liquid fraction 20′ and a second lower liquid fraction 22′.Generally speaking, the secondary separation occurring in trough 26 willnot be complete and, as a matter of practice, residual amounts of theorganic phase will be retained in the second lower liquid fraction 22′.

[0025] The second upper liquid fraction 20′ is drained from the trough26 by the first lighter fraction drain 38. However, since the inlet end40 of first drain 38 is located above the second interface 24′, thefirst drain 38 removes primarily only the second upper liquid fraction20′, leaving behind the second lower liquid fraction 22′. The secondupper liquid fraction 20′ removed from the trough 26 may thereafter bedischarged into the lighter fraction container 62 and held forsubsequent processing. The second lower liquid fraction 22′ contained intrough 26 is withdrawn via the two sump drains 44 and 46 and thereafterdischarged into the two respective column separators 48 and 50. Eachcolumn separator 48, 50 effects a tertiary separation of the organic andaqueous phases by allowing the second lower liquid fraction 22′ drawnfrom the trough 26 to separate into a third upper liquid fraction 20″and a third lower liquid fraction 22″. The third upper liquid fraction20″ (comprising primarily the organic phase, but with some residualaqueous phase contained therein) is returned to the trough 26 via thelighter fraction return lines 52 and 58 associated with the respectivecolumn separators 48 and 50. The third lower liquid fraction 22″ isdrained from the column separators 48 and 50 and is discharged into thesecond settling tank 56.

[0026] The second settling tank 56 effects a quaternary separation ofthe organic and aqueous phases by allowing the third lower liquidfraction 22″ to separate into a fourth upper liquid fraction 20″′ and afourth lower liquid fraction 22″′. The fourth upper liquid fraction 20″′may be directed to the lighter fraction container 62, whereupon it maybe held for further processing. The fourth lower liquid fraction 22″′may be combined with the raffinate removed from the drain 64 associatedwith the second trough 36.

[0027] The loaded organic phase (i.e., the lighter liquid 14) recoveredby the liquid separation apparatus 10 and contained in tank 62 maythereafter be processed to recover the copper ions contained therein byany of a wide range of processes that are well known in the art. Forexample, referring back now to FIG. 4, in one preferred embodiment, theloaded organic phase 14 contained in container 62 may be “stripped” bycombining it with a suitable electrolyte. The electrolyte strips thecopper ions from the loaded organic phase to produce barren or“stripped” organic extractant and a pregnant electrolyte. The strippedorganic extractant may then be recycled and reused in the SX processjust described. The pregnant electrolyte may then be directed intosuitable tanks or cells wherein the copper ions contained in thepregnant electrolyte are plated onto cathode mother blanks in a processcommonly referred to as electrowinning. However, since such subsequentprocessing steps (e.g., stripping and electrowinning) are well-known inthe art and are not required to practice the present invention, suchsubsequent processing steps will not be described in further detailherein.

[0028] A significant advantage of the liquid separation apparatus 10according to the present invention is that it effectively removesentrained aqueous from the organic phase, thereby reducing oreliminating the problems associated with the presence of entrainedaqueous in the loaded organic phase, including problems associated withthe presence of chloride and/or iron in the pregnant electrolytesolution. The present invention also requires no moving parts, and isthus easy and inexpensive to install and maintain.

[0029] Having briefly described the liquid separation apparatus andmethod according to the present invention, as well as some of their moresignificant features and advantages, the various embodiments of themethod and apparatus for separating a heavier liquid and a lighterliquid will now be described in detail. However, before proceeding withthe description, it should be noted that while the present invention isshown and described herein as it could be used to separate the organicphase from the aqueous phase in a solvent extraction process forremoving copper from raw ore, it is not limited to use with anyparticular process. Indeed, the present invention could be used in anyof a wide range of applications and processes wherein it would bedesirable to effect a more complete separation of lighter and heavierliquids. Consequently, the present invention should not be regarded aslimited to the particular examples and applications shown and describedherein.

[0030] With the foregoing considerations in mind, the liquid separationapparatus 10 may comprise a settling tank 12 sized to receive thelighter liquid 14 and the heavier liquid 16. By way of example, in onepreferred embodiment, the lighter liquid 14 may comprise a loadedorganic extractant (e.g., an organic phase), whereas the heavier liquid16 may comprise an aqueous phase or raffinate. In the embodiment shownand described herein, the settling tank 12 may be integrated with amixing container 15 in which the pregnant leach solution 11 may becombined with the barren organic extractant 13. The mixing container 15may be provided with a mechanical mixer or agitator 17 to morethoroughly mix the pregnant leach solution 11 with the barren organicextractant 13.

[0031] As was discussed above, the mixing of the pregnant leach solution11 with the barren organic extractant 13 results in the formation of aloaded organic extractant (i.e., the organic phase) and a raffinate(i.e., the aqueous phase). The loaded organic extractant will bereferred to hereinafter as the lighter liquid 14, whereas the raffinatewill be referred to hereinafter as the heavier liquid 16. The mixture ofthe lighter and heavier liquids 14 and 16 may be directed to thesettling tank 12 after passing through one or more “picket fences”baffles 66.

[0032] Continuing now with the description, the settling tank 12 extendsessentially from the picket fence or baffle 66 to an outlet end 28. Thesettling tank 12 includes a quiescent zone 18 therein which permits theformation of a first upper liquid fraction 20 and a first lower liquidfraction 22. A first interface 24 separates the first upper and lowerliquid fractions 20 and 22 and generally becomes more defined toward theoutlet end 28 of settling tank 12.

[0033] The settling tank 12 may comprise any of a wide range ofdimensions and holding capacities depending on the requirements of theparticular process in which the liquid separation apparatus 10 is to beemployed. Consequently, the present invention should not be regarded aslimited to a settling tank 12 having any particular length, width, andheight dimensions, nor any particular volume capacity. However, by wayof example, in one preferred embodiment, the settling tank 12 comprisesa generally rectangular structure having a length 78 of about 105 feet,a height 80 of about 3.5 feet, and a width of about 45 feet. Thesettling tank 12 may be fabricated from any of a wide range of materials(e.g., metals or concretes) suitable for the intended application. Byway of example, in one preferred embodiment, the settling tank 12 ismanufactured from 316 stainless steel, although other materials may alsobe used.

[0034] A weir 30 may be positioned adjacent the outlet end 28 ofsettling tank 12 and extends above the level of the first interface 24separating the first upper and lower liquid layers 20 and 22. SeeFIG. 1. Accordingly, the weir 30 allows substantially the first upperliquid fraction 20 to be removed or decanted from the settling tank 12.By way of example, in one preferred embodiment, the weir 30 is locatedabout 8-10 inches above the first interface 24, although the weir 30 maybe positioned at other locations, so long as it is above the level ofthe first interface 24. A trough 26 positioned adjacent the weir 30receives the first upper liquid fraction 20 discharged over the weir 30.As will be described in greater detail below, the trough 26 effects asecondary separation of the lighter and heavier liquids 14 and 16 bypermitting the first upper liquid fraction 20 to separate into a secondupper liquid fraction 20′ and a second lower liquid fraction 22′. Thesecond upper and lower liquid fractions 20′ and 22′ may become separatedby a second interface 24′, as shown in FIGS. 1 and 2.

[0035] The trough 26 may have overall dimensions and a volume capacitycommensurate with the overall volume flow-rate of the first upper liquidfraction 20 that is expected to be produced by the settling tank 12.Consequently, the present invention should not be regarded as limited toa trough 26 having any particular dimensions or volume capacity.However, by way of example, in one preferred embodiment, the firsttrough 26 may have a width 68 (FIG. 2) commensurate with the width ofthe settling tank 12 (e.g., about 45 feet) and a length 70 (FIG. 3) ofabout 39 inches. The height 72 of the weir 30 may be about 22 inches,whereas the height 74 of the end wall 76 is about 33 inches. The firsttrough 26 may be made from any of a wide range of materials (such asmetals or plastics) suitable for the intended application. By way ofexample, in one preferred embodiment, the first trough 26 is fabricatedfrom 316 stainless steel.

[0036] The trough 26 may be provided with a first lighter fraction drain38 having an inlet end 40 that is located at an elevated position abovethe floor 42 of trough 26. Generally speaking, it will be preferable toposition the elevated inlet end 40 of the first drain 38 so that it islocated above the second interface 24′ separating the second upper andlower liquid fractions 20′ and 22′, respectively. By way of example, inone preferred embodiment, the inlet end 40 of first drain 38 ispositioned about 15 inches above the floor 42 of the trough 26. Thefirst drain 38 may discharge into a lighter fraction container 62, asbest seen in FIG. 1.

[0037] The trough 26 may also be provided with a pair of sump drains ortraps 44 and 46 located on the bottom 42 of trough 26. In the embodimentshown and described herein, the sump drains or traps 44 and 46 arepositioned on either side of the first drain 38. Alternatively, the sumpdrains 44 and 46 may be located at any convenient position along thebottom 42 of trough 26. In still another arrangement, the sump drains 44and 46 may be located on the lower portions of the sides of trough 26,so long as they are located below the second interface 24′. Referringnow primarily to FIG. 3, the sump drains 44 and 46 are essentiallyidentical and may comprise a sump portion 82 that opens into the trough26. Drain pipes 90, 92 connected to the respective sump drains 44, 46may be used to direct liquid from the sump drains 44, 46 to therespective column separators 48, 50.

[0038] The sump drains 44, 46 may be made from any of a wide range ofmaterials, such as metals or plastics, suitable for the intendedapplication. Moreover, each sump drain 44, 46 may be sized to removeliquid at a rate sufficient to prevent the trough 26 from overflowing.Consequently, the present invention should not be regarded as limited tosump drains being fabricated from any particular material or to anyparticular size. By way of example, in one preferred embodiment, bothsump drains 44, 46 are fabricated from 316 stainless steel. Each sumpdrain 44, 46 may have a length 84 of about 36 inches, a width 86 ofabout 4 inches, and a depth 88 of about 4 inches. Drain pipes 90 and 92may comprise pipes fabricated from PVC (polyvinylchloride) plastic andhaving diameters of about 2 inches. Alternatively, pipes fabricated fromother materials or having different sizes could also be used.

[0039] Referring back now to FIG. 1, each sump drain 44, 46 dischargesinto a respective column separator 48, 50, each of which performs atertiary separation of the lighter and heavier liquids 14, 16 containedin the second lower liquid fraction 22′ drawn from the trough 26. Thatis, each column separator 48, 50 allows the second lower fraction 22′drawn from the trough 26 to form a third upper liquid fraction 20″ and athird lower liquid fraction 22″. A third interface 24″ may form betweenthe third upper and lower liquid fractions 20″ and 22″, respectively.The first column separator 48 may be provided with a lighter fractionreturn line 52 located generally above the third interface 24″ forreturning to the trough 26 quantities of the third upper liquid fraction20″. Column separator 48 may also be provided with a drain line 54 fordraining the third lower liquid fraction 22″ from the column separator48. The drain line 54 may discharge the third lower liquid fraction 22″into a second settling tank 56. The second column separator 50 may beessentially identical to the first column separator 48 and may include alighter fraction return line 58 located above the third interface 24″for returning to the trough 26 quantities of the third upper liquidfraction 20″. A drain line 60 may be used to drain to the secondsettling tank 56 the third lower fraction 22″ from the second columnseparator 50.

[0040] The first and second column separators 48 and 50 may comprise anyof a wide range of column separators well-known in the art and that arereadily commercially available. Consequently, the present inventionshould not be regarded as limited to any particular type or style ofcolumn separator. By way of example, in the embodiment shown anddescribed herein, each column separator 48, 50 may comprise a generallycylindrical member having a height of about 5 feet and a diameter ofabout 8 inches. The column separators 48 and 50 may be made from any ofa wide range of materials suitable for the intended application, aswould be obvious to persons having ordinary skill in the art. By way ofexample, each column separator 48, 50 in one preferred embodiment isfabricated from HDPE (high-density polyethylene), although othermaterials could also be used. The various drain lines 52, 54, 58, and 60may comprise PCV pipes having diameters of about 1 inches, althoughpipes fabricated from other materials and having different diameterscould also be used.

[0041] The drain lines 54 and 60 from the first and second columnseparators 48 and 50 may be connected to the second settling tank 56.The second settling tank 56 may be used to perform a quaternaryseparation of the lighter and heavier liquids 14 and 16 contained in thethird lower liquid fraction 22″ drawn from the column separators 48 and50. That is, the second settling tank 56 permits the third lower liquidfraction 22″ drawn from the column separators 48 and 50 to separate intoa fourth upper liquid fraction 20″′ and a fourth lower liquid fraction22″′. The fourth upper and lower liquid fractions 20″′ and 22″′ maybecome separated by a fourth interface 24″′. The fourth upper liquidfraction 20″′ may thereafter be directed to the lighter fractioncontainer 62. The fourth lower liquid fraction 22″′, which comprisesprimarily the heavier liquid 16 (e.g., the aqueous phase or raffinate),may be withdrawn from the second settling tank 56 and reused ordiscarded, depending on the requirements of the particular process.

[0042] The second settling tank 56 and the lighter fraction container 62may comprise any of a wide range of containers having sizes suitable forthe liquid flow rates expected in the particular process. However, sincesuch containers are well-known in the art and are readily commerciallyavailable, the second settling tank 56 and lighter fraction container 62utilized in one preferred embodiment of the invention will not bedescribed in further detail herein.

[0043] Still referring to FIG. 1, the liquid separation apparatus 10 mayalso be provided with a heavier fraction container or tank 32 that isfluidically connected to the settling tank 12 so that the first lowerliquid fraction 22 from the settling tank 12 flows into the heavierfraction container or tank 32. In one preferred embodiment, thecontainer 32 comprises an integral extension of the settling tank 12,although other configurations are possible, as would be obvious topersons having ordinary skill in the art. The container 32 may beprovided with a second weir 34 which, together with the container 32,defines a second trough 36. The second trough 36 may be provided with adrain 64 for removing the heavier liquid 16 from the second trough 36.The heavier liquid 16 (e.g., the aqueous phase or raffinate) withdrawnfrom the second trough 36 may be combined with the heavier liquid 16withdrawn from the second settling tank 56 and reused or discarded, asthe case may be.

[0044] Operation of the liquid separation apparatus 10 according to thepresent invention may be understood by considering its operation in asolvent extraction (i.e., SX) process of the type that may be used toremove copper from raw ore. Referring now to FIG. 4, the first step insuch a process typically involves contacting the raw ore with an initialleaching solution or lixiviant. The lixiviant leaches copper ions fromthe ore to generate a lixiviant product or “pregnant leach solution” 11.The pregnant leach solution 11 thereafter may be combined with a barrenorganic extractant 13 in container 15. See also FIG. 1. During themixture of these components, copper ions contained in the pregnant leachsolution 11 are transferred directly into the barren organic extractant13. As a result, an organic phase and an aqueous phase are produced. Theorganic phase comprises primarily the loaded organic extractant (whichcontains copper ions captured from the pregnant leach solution). Theaqueous phase (also known as raffinate) comprises primarily thelixiviant solution which lacks any substantial or appreciable amounts ofdissolved copper therein.

[0045] In the foregoing SX process, the organic phase is generally lessdense than the aqueous phase and the two phases tend to separate intodiscrete layers based on substantial differences in specific gravity andother physical factors (e.g., polarity). However, as a matter ofpractice, some of the aqueous phase (i.e., the raffinate) tends toremain with the organic phase (i.e., the loaded organic extractant). Theliquid separation apparatus 10 according to the present invention isused to separate the aqueous and organic phases.

[0046] Referring now to FIG. 1, the pregnant leach solution 11 may becombined with the appropriate quantity of barren organic extractant 13in the container 15, whereupon they are mixed together with the aid ofthe mixer or agitator 17. During the mixing process, copper ionscontained in the pregnant leach solution are transferred to the barrenorganic extractant 13 to form the organic phase (i.e., the lighterliquid 14) and the aqueous phase (i.e., the heavier liquid 16). The twophases (i.e., the organic and aqueous) resulting from the mixture of thepregnant leach solution 11 and barren organic extractant 13 arethereafter allowed to enter the settling tank 12 after passing throughthe baffle or “picket fence” 66 separating the settling tank 12 from themixing container 15. Once in the settling tank 12, the organic phase(i.e., the lighter liquid 14) begins to separate from the aqueous phase(i.e., the heavier liquid 16), ultimately forming the first upper liquidfraction 20 and the first lower liquid fraction 22. In the example SXprocess shown and described herein, the first upper liquid fraction 20will consist primarily of the organic phase with residual amounts of theaqueous phase contained therein, whereas the first lower liquid fraction22 will consist primarily of the aqueous phase with residual amounts ofthe organic phase contained therein.

[0047] The first weir 30 permits the first upper liquid fraction 20contained within the quiescent zone 18 of settling tank 12 to decantinto trough 26. The trough 26 effects a secondary separation of theorganic and aqueous phases by allowing the first upper liquid fraction20 drawn from the settling tank 12 to separate into a second upperliquid fraction 20′ (comprising primarily the organic phase) and asecond lower liquid fraction 22′ (comprising primarily the aqueousphase). Generally speaking, the secondary separation occurring in trough26 will not be complete and residual amounts of the organic phase willbe retained in the second lower liquid fraction 22′.

[0048] The second upper liquid fraction 20′ is drained from the trough26 by the first lighter fraction drain 38. However, since the inlet end40 of first lighter fraction drain 38 is positioned above the secondinterface 24′, the first drain 38 removes primarily only the secondupper liquid fraction 20′. The second upper liquid fraction 20′ removedfrom the trough 26 by the first drain 38 thereafter may be dischargedinto the lighter fraction container 62 and held for subsequentprocessing. The second lower liquid fraction 22′ from trough 26 iswithdrawn via the two sump drains 44 and 46 and thereafter dischargedinto the two respective column separators 48 and 50. Each columnseparator 48, 50 effects a tertiary separation of the organic andaqueous phases by allowing the second lower liquid fraction 22′ from thetrough 26 to separate into a third upper liquid fraction 20″ and a thirdlower liquid fraction 22″. The third upper liquid fraction 20″(comprising primarily the organic phase, but with some residual aqueousphase contained therein) is returned to the trough 26 via the lighterfraction return lines 52 and 58. The third lower liquid fraction 22″ isdrained from the column separators 48 and 50 and is discharged into thesecond settling tank 56.

[0049] The second settling tank 56 effects a quaternary separation ofthe organic and aqueous phases by allowing the third lower liquidfraction 22″ to separate into a fourth upper liquid fraction 20″′ and afourth lower liquid fraction 22″′. The fourth upper liquid fraction 20″′may be directed to the lighter fraction container 62 and held forfurther processing. The fourth lower liquid fraction 22″′ may becombined with the raffinate removed from the drain 64 associated withthe second trough 36.

[0050] The loaded organic phase (i.e., the lighter liquid 14) recoveredby the liquid separation apparatus 10 and contained in tank 62thereafter may be processed to recover the copper ions containedtherein. For example, referring back now to FIG. 4, in one preferredembodiment, the loaded organic phase 14 contained in tank 62 may be“stripped” by combining it with a suitable electrolyte. The electrolytestrips the copper ions from the loaded organic phase to produce barrenor stripped organic extractant and a pregnant electrolyte. The strippedorganic extractant may then be recycled and reused in the SX processjust described. The pregnant electrolyte may then be directed intosuitable tanks or cells wherein the copper ions contained in thepregnant electrolyte are plated onto cathode mother blanks in a processknown generally as electrowinning.

[0051] It is contemplated that the inventive concepts herein describedmay be variously otherwise embodied and it is intended that the appendedclaims be construed to include alternative embodiments of the inventionexcept insofar as limited by the prior art.

What is claimed is:
 1. A method for separating a lighter liquid from a heavier liquid, comprising: introducing the lighter liquid and the heavier liquid into a settling tank; permitting the lighter liquid and the heavier liquid to form first upper and lower liquid fractions, the first upper liquid fraction comprising the lighter liquid with residual amounts of the heavier liquid contained therein; permitting the first upper liquid fraction in the settling tank to decant into a trough; permitting the first upper liquid fraction decanted into the trough to form second upper and lower liquid fractions, the second lower liquid fraction comprising the heavier liquid with residual amounts of the lighter liquid contained therein; draining the second lower liquid fraction from the trough; and permitting the second lower liquid fraction drained from the trough to form third upper and lower liquid fractions.
 2. The method of claim 1 , further comprising the step of permitting the second upper liquid fraction in the trough to decant into a lighter fraction container.
 3. The method of claim 2 , further comprising the step of permitting the third upper liquid fraction to decant into the trough.
 4. The method of claim 3 , further comprising the step of permitting the third lower liquid fraction to form fourth upper and lower liquid fractions.
 5. The method of claim 4 , further comprising the step of permitting the fourth upper liquid fraction to decant into the lighter fraction container.
 6. The method of claim 1 , further comprising the step of permitting the third lower liquid fraction to form fourth upper and lower liquid fractions.
 7. The method of claim 6 , wherein the step of permitting the third lower liquid fraction to form fourth upper and lower liquid fractions comprises the step of permitting an interface substantially separating the fourth upper and lower liquid fractions to form.
 8. The method of claim 6 , wherein the step of permitting the third lower liquid fraction to form fourth upper and lower liquid fractions comprises the steps of: permitting the third lower liquid fraction to decant into a second settling tank; and permitting an interface substantially separating the fourth upper and lower liquid fractions to form within the second settling tank.
 9. The method of claim 8 , further comprising the steps of: draining the fourth lower liquid fraction from the second settling tank; and permitting the fourth upper liquid fraction to decant into a lighter fraction container.
 10. The method of claim 1 , wherein the step of introducing the lighter liquid and heavier liquid into a settling tank comprises the step of permitting the lighter liquid and the heavier liquid to pass through a baffle, the lighter liquid and the heavier liquid entering the settling tank by passing through the baffle.
 11. The method of claim 1 , wherein the step of permitting the lighter liquid and the heavier liquid to form first upper and lower liquid fractions comprises the step of permitting an interface substantially separating the first upper and lower liquid fractions to form within the settling tank.
 12. The method of claim 11 , wherein the interface forms within a quiescent zone within the settling tank.
 13. The method of claim 1 , wherein the step of permitting the first upper liquid fraction in the settling tank to decant into a trough comprises the step of permitting substantially the first upper liquid fraction in the settling tank to be discharged over a weir into the trough.
 14. The method of claim 1 , further comprising the step of draining the first lower liquid fraction from the settling tank.
 15. The method of claim 14 , wherein the step of draining the first lower liquid fraction from the settling tank comprises the step of permitting the first lower liquid fraction in the settling tank to flow into a heavier fraction tank.
 16. The method of claim 14 , wherein the step of draining the first lower liquid fraction from the settling tank comprises the step of permitting the first lower liquid fraction in the settling tank to decant into a second trough.
 17. The method of claim 16 , wherein the step of permitting the first lower liquid fraction in the settling tank to decant into a second trough comprises the step of permitting substantially the first lower liquid fraction in the settling tank to be discharged over a second weir into the second trough.
 18. The method of claim 1 , wherein the step of permitting the first upper liquid fraction decanted into the trough to form second upper and lower liquid fractions comprises the step of permitting an interface substantially separating the second upper and lower liquid fractions to form within the trough.
 19. The method of claim 1 , wherein the step of draining the second lower liquid fraction from the trough comprises the step of permitting substantially the second lower liquid fraction to flow into a column separator.
 20. The method of claim 1 , wherein the step of permitting the second lower liquid fraction drained from the trough to form third upper and lower liquid fractions comprises the step of permitting an interface substantially separating the second upper and lower liquid fractions to form. 